Mount Prospect, Illinois 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

654
FXUS63 KLOT 252032
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
232 PM CST Sun Jan 25 2026

.KEY MESSAGES...

- Snow, falling heavily at times with rates up to around an inch
  per hour, will affect areas near the lake through this
  evening. Lake effect will shift east from IL into IN by early
  evening and east of Porter County by around midnight.

- Snow will end away from lake Michigan by early evening.

- Dangerously cold wind chills expected late tonight and Monday
  morning.

&&

.DISCUSSION...
Issued at 232 PM CST Sun Jan 25 2026

Back edge of the synoptic snow is moving east across the area
this afternoon and should continue eastward with snow ending
from east to west through early evening. Lake enhanced snow
will transition to pure lake effect snow by early evening as the
synoptic snows move off to the east.

Recent ACARs soundings out of MDW depict a sharp inversion
around 5kft, so lake induced instability is shallow, but very
strong. Aided by the synoptic snows, the lake enhanced snow this
morning has been fallen heavily at times with snowfall rates up
to an inch per hour. Lake enhanced snow has penetrated as far
inland as Kankakee County, though anticipate the inland
penetration and probably the intensity of the snow will decrease
a bit as the seeder-feeder process ends as synoptic snows shift
east.

Any potential decrease in intensity of the lake effect looks to
be short lived early this evening as mid-upper level trough
approaches this evening. Height falls in advance of the trough
are progged to result in rising inversion heights and deepening
lake induced convective layer. In addition to the rising
inversion height, the nocturnal strengthening of the land breeze
convergence zone should lead to the development of an intense
narrow band of heavy lake effect snow as the focus shifts east
into Porter County.

Lake effect parameters are forecast to become exceptionally
favorable for a very intense lake effect snow band, with the
main question for our CWA being how quickly it organizes and
intensifies. By late evening and especially after midnight, it
wouldn`t be at all surprising to see 2-3"+ per hour snowfall
rates with the band. The potential ramp up in intensity of the
lake effect band looks to occur far enough west to justify the
earlier upgrade of Porter County to a winter storm warning and
bumping up snowfall totals there. The ceiling is high with this
event, should the band intensify on the earlier end of the
spectrum and particularly if it were to slow its progression
across Porter County, then double digit additional snowfall
totals would be possible. On the other end of the spectrum, if
the band were to remain more progressive and the intensity were
to not take off until it is east of Porter County, then the
additional snowfall amounts in northern Porter County could end
up more in the 2-4" range.

In the wake of the snow, skies will clear out and with many
areas now covered in a fresh blanket of fluffy new snow, would
anticipate temps to respond nicely to the cold air advection.
Made no significant changes to temps tonight, but did nudge high
temps down a bit for Monday. Northwest winds 10-15 mph should
send wind chills down 15 to 25 below zero late tonight into
Monday morning, so Cold Weather Advisory looks to be in good
shape with no changes planned.

- Izzi


Monday night through Saturday:
Issued at 340 AM CST Sun Jan 25 2026

The next robust clipper system will descend out of Saskatchewan
on Monday and then across the Upper Great Lakes region Monday
night into Tuesday morning. Seeing generally good agreement on
the handling of this feature, with guidance taking the core of
the most robust mid-level height falls to our north. That said,
the magnitude of large scale forcing is quite robust.

While guidance doesn`t appear to formally produce snow accums
in our area, forecast soundings from various guidance would
support flurries or light snow with saturation down under
850-900 mb, particularly late Monday night through Tuesday
morning across roughly the northeastern half of the CWA and
especially across far northeast Illinois. Thereafter, steepening
0-1 km lapse rates in the wake of the associated surface front
look to drive increasing saturation into the base of a fairly
deep dendritic growth zone late Tuesday morning and afternoon.
Low-level f-gen is generally transient or non- existent,
suggesting the threat for bonafide squalls is low, but seeing a
signal of NW-SE oriented streaks of QPF in some of the guidance
which is likely indicative of isolated-scattered gusty snow
showers through Tuesday morning and early afternoon. At this
time, have not formally added a snow shower mention to the
grids, but if trends continue, will need to consider a weather
mention during this time frame. Can`t totally rule out some
disorganized LES meandering into far NE Porter County Tuesday
afternoon given slightly more NW oriented boundary layer flow,
but the bulk of any lake effect looks to remain decidedly to our
east.

A reinforcing shot of cold air will send low temperatures Tuesday
night back to either side of 0 degrees with colder wind chills
given a steady westerly breeze.

The next robust disturbance arrives late Tuesday night into
Wednesday. Guidance appears to be settling in on a slightly
farther south track at this point, although there`s generally
low confidence this far out with these types of systems. Will be
a period to watch as this would be another instance of light
snow accumulations falling into a very cold airmass where road
treatments would likely be mostly ineffective. Strongest signal
for light snow accumulations into Wednesday afternoon are
roughly south (to well south) of I-80.

Lots of spread in the handling of the general large scale
synoptic pattern by the end of the week. Still seeing a signal
(ephemeral as it may be from run-to-run) of a potentially
interesting set up towards Thursday night - Friday involving an
intense shortwave trough pushing southwestward across the Great
Lakes which would turn the lake effect snow machine back on in
the general region.

Otherwise, continued cold is the message through next week.
Could be some periods where we`re flirting with Cold Weather
headline criteria at times, but nothing to the level of what we
experienced this past Friday/Saturday.

Carlaw

&&

.AVIATION /18Z TAFS THROUGH 00Z TUESDAY/...
Issued at 1138 AM CST Sun Jan 25 2026

Aviation forecast concerns:

- Snow gradually ending this afternoon across the Chicago
  terminals, with periods of LIFR possible mainly for MDW/GYY.

Lake-enhanced snowfall will persist across the Chicago terminals
this afternoon, though will gradually shift southeast into
northwest IN late. Current radar imagery depicts the northern
edge of the heavier lake-banding over ORD, though with a slow
southeastward drift expect vis may improve from their current
3/4SM fairly soon. MDW and GYY are most likely to see
intermittent periods of sub-1SM vis through mid-late afternoon
as these bands shift. Improving conditions can then be expected
into early this evening. DPA will likely experience some
occasional light snow with MVFR cigs early this afternoon while
only flurries are expected at RFD.

Surface winds generally from the north-northwest will become
somewhat blustery with gusts 20-25 kts this afternoon, gradually
backing northwest this evening and eventually more westerly
midday Monday. The exception will be for MDW and GYY this
afternoon, where winds will initially be from the northeast in
association with the lake-effect convergent zone.

Ratzer

&&

.HYDROLOGY...
Issued at 230 PM CST Fri Jan 23 2026

River gauges, reports from local officials, and reports from
trained ice spotters continue to indicate a few ice jams across
the area due to the significant increase in river ice over
recent days. With continued cold weather into next week,
conditions will remain favorable for river ice formation. While
no widespread flooding is expected, localized ice jams may
occur.

- NWS Chicago

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...Cold Weather Advisory from midnight tonight to noon CST Monday
     for ILZ003-ILZ004-ILZ005-ILZ006-ILZ008-ILZ010-ILZ011-
     ILZ012-ILZ013-ILZ019-ILZ020-ILZ021-ILZ023-ILZ032-ILZ033-
     ILZ039-ILZ103-ILZ104-ILZ105-ILZ106-ILZ107-ILZ108.

     Winter Weather Advisory until 6 PM CST this evening for ILZ006-
     ILZ013-ILZ019-ILZ020-ILZ021-ILZ023-ILZ032-ILZ033-ILZ039-
     ILZ106-ILZ107-ILZ108.

     Winter Storm Warning until 4 PM CST this afternoon for ILZ103-
     ILZ104-ILZ105.

IN...Cold Weather Advisory from midnight CST /1 AM EST/ tonight to
     noon CST /1 PM EST/ Monday for INZ001-INZ002-INZ010-
     INZ011-INZ019.

     Winter Weather Advisory until midnight CST tonight for INZ001.

     Winter Storm Warning until midnight CST tonight for INZ002.

     Winter Weather Advisory until 9 PM CST /10 PM EST/ this
     evening for INZ010-INZ011-INZ019.

LM...Small Craft Advisory until 6 PM CST Tuesday for the IL and IN
     nearshore waters.

&&

$$

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